ADC Therapeutics has announced a voluntary pause in the enrolment of new patients in the Phase 2 LOTIS-9 trial investigating the combination of ZYNLONTA (loncastuximab tesirine-lpyl) and rituximab (Lonca-R) in unfit or frail patients with previously untreated diffuse large B-cell lymphoma (DLBCL).

The decision was made by the Swiss biotechnology firm after consultation with the data monitoring committee regarding results aggregate data from 40 patients enrolled thus far, which showed potentially excessive respiratory-related events.

ADC found seven grade 5 respiratory-related treatment-emergent AEs (TEAEs), as well as 5 grade or grade 4 respiratory TEAEs.

According to the investigator’s assessment, six of the seven grade 5 fatal events and 11 of the 12 events were determined to be improbable or unrelated to the study drug.

Since then, four of the five grade 3 or grade 4 incidents have ended, and the patients have finished their prescribed course of treatment. Further research is being done to determine the reason for these occurrences.

ADC Therapeutics CEO Ameet Mallik said: “Our top priority is the safety of every patient who participates in our clinical trials. Given the aggregate of the respiratory-related events seen in the trial, we implemented a voluntary pause of enrolment to allow for a thorough investigation of the data set.

“This trial includes a very difficult-to-treat patient population with limited treatment options, and we will provide an update on next steps when available.”

The firm’s decision to stop enrolment in the LOTIS-9 trial gives time to assess the data around the TEAEs and choose the appropriate course of action.

ADC has informed all study investigators and regulatory agencies, including the European Medicines Agency (EMA) and the US Food and Drug Administration (FDA) about its decision to suspend enrolment.

The company does not anticipate reporting any additional trial-related data by the end of the year.

Recently, ADC and Swedish Orphan Biovitrum have signed an exclusive license agreement for Zynlonta.